Origin: North America (native in Ontario)
Trembling aspen is a medium-sized tree with a straight, slim trunk and a narrow crown.Read more about Tree, Bark, Twigs
Leaves are oval to round with a sharply tapering tip and fine teeth along the edges. The leaf stalk is flattened allowing the leaves to tremble.Read more about Leaves
Flowers are tiny, clustered in dense catkins, borne in early spring, before the leaves emerge.Read more about Flowers
Fruits are small green capsules borne in catkins.Read more about Fruit
Trembling aspen is a medium-sized tree, up to 25 m (82') in height and 40 cm (15 3/4") in diameter, with a straight, slim trunk and a narrow crown.
Twigs are slender, shiny brown, sometimes covered with a waxy bloom, and with oval pores (lenticels). The buds are conical, with pointed tips that curve inward.
Leaves are 3 - 7 cm (1 1/8" - 2 3/4") long and almost as wide with a sharply tapered tip and fine teeth along the edges. The base of the leaf may be straight, rounded or slightly heart-shaped.
As with other trees of the Populus genus, the leaf stalk is flattened allowing it tremble in the slightest breeze.
Flowers are tiny, clustered in dense catkins. Male and female catkins are borne on separate trees in early spring before the leaves emerge.
Catkins are 4 - 8 cm (1 1/2" - 3") long when they reach their full length. These catkins bear female flowers with red stigmas.
These catkins bear male flowers with blackish anthers. The third catkin on this twig is still in bud and has yet to lengthen.
Capsules are green, pointed, hairless, 5 - 7 mm (about 1/4") long. They release their seeds in May or June.
Trembling aspen is one of the most widely distributed tree species in North America, extending from Alaska to Newfoundland and as far south as Mexico. It is native to all of Canada's forest regions, except along the Pacific coast.
Longevity and clones
Trembling aspens are relatively short-lived trees, with an average lifespan of up to up to 80 years in the wild. However, they reproduce clonally by root sprouts to form large long-lived stands that are, essentially, one large plant. One such stand in Utah, occupying about 100 acres, was estimated to consist of about 47,000 stems. The root system of a stand found in Minnesota was estimated to be approximately 8,000 years old. Stands such as these are among the largest and oldest living things on Earth and are thought to have originated after the Pleistocene ice sheet receded, leaving the soil exposed.
Trembling aspen is intolerant of shade and cannot grow in dense forests. Rather, trembling aspen is an early successional tree, meaning it is one of the first species to grow in a forest that has experienced some kind of disturbance, such as logging or fire.
Derivation of names
The genus name, Populus, is the classical name for the poplar tree. The species name, tremuloides, comes from the Latin tremulus, meaning trembling, and the Greek oides, meaning resembling, because of its similarity to quaking aspen (Populus tremula), a closely related European species that is also known for its trembling or fluttering leaves.
Trembling aspen wood is important for the manufacture of paper and chipboard. It has also been used to make matchsticks, crates, and fences.
Trembling aspen is an important food source for wildlife. Deer, moose, beavers, and snowshoe hares eat the bark and twigs, while many species of birds eat the buds and seeds. As with many natural pests, some of the pests that affect trembling aspen can benefit biodiversity. For example, heart-rot fungus (Fomes ignarius populinus) causes the inner wood of trembling aspen to decay, creating cavities that can be used as shelter by woodpeckers, owls, flying squirrels, and other wildlife. Hypoxylon canker, a native disease that spreads through a clonal colony until the whole grove dies, hastens the succession to a mature forest.
Trembling aspen's place in Toronto's urban forest
Trembling aspen provides a unique textural component to the urban forest canopy with its fluttering leaves. It is a short-lived, early successional species, among the first tree species to colonize open spaces. Its light shade allows longer-lived species to spring up beneath them. In Toronto, mature aspens are found in small groves in or along the edge of more mixed forests. Younger groves are becoming increasingly common in more open places as it has been extensively used in restoration projects over the last decade or two. It is often but not exclusively found on moist sites.
Landscape value and potential for home planting
In urban settings, trembling aspen is best enjoyed in natural park-like settings. It is not widely used as an ornamental tree, mainly because of its fairly short lifespan (as little as 25 years, up to about 80 years); its fast-growing, spreading and sprouting roots; and because it is vulnerable to many diseases and pests that cause cankers, defoliation, and boring holes in the trunk.
Pests and diseases: For information on pests and diseases of trembling aspen, see Natural Resources Canada fact sheet. See also above under Wildlife Value.
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